1. Field of the Invention
The present invention relates to a method of detecting a defect area of a disk without mistakes during data recording on a writable disk.
2. Description of the Related Art
A physical damage such as scratch etc. has an effect on a few or some physical tracks. Especially, a center area of a defect zone has the worst effect on data recording.
If a high-speed data writing is tried at a center area of such a defect zone, a tracking servo control might be terminated so that a recording operation would be interrupted abruptly. In the case that a recording operation is abnormally ended, it is impossible to resume data recording from the abnormally-ended recording position, therefore, data recording must be re-started from the beginning inevitably. However, because a once-writable disk, namely, a CD-R can not be rewritable, it is obliged to be thrown away.
For resolving this problem, various methods are being developed. Almost of the various methods aim at successful data recording even in a defect area by detecting a defect area and reducing recording speed at the detected defect area. One of the various methods uses level of a tracking error (TE) signal.
In the method using level of a TE signal, the level of a TE signal is always being monitored while data is recorded on a writable disk at a predetermined recording speed, and if the monitored level is greater than a preset limit level a current recording area is regarded as defect. In other words, if the TE signal looks unstable a current recording area is regarded as defect so that a current recording speed is decreased to adequate one. After speed reduction, recording operation is proceeded.
However, the TE signal may be unstable instantaneously due to a mechanical shock or disturbance from the outside, therefore, if only level of the TE signal is used in determination of a defect area, a normal recording area may be mistakenly regarded as defect, which leads unnecessary writing speed reduction.